Longest Period I Have Ever Had- What's Wrong?

Brittany • Sat, Apr 04

I started my period on the 19th of March and it was "officially" over on the 25st, but I still had lots of spotting and now I'm heavy again (as it would be the first day of my cycle) and I have the worst cramps in my back and stomach. I am on the pill, but I missed a couple of days here and there throughout my pack. I would just like to know why I have my period again in this short of a time period in between cycles. Any answers or theories would be appreciated.